The present invention relates to a new class of nucleoside analogues and to their therapeutic use in the prophylaxis and treatment of viral infection for example by varicella zoster virus (VZV). Varicella zoster virus is the aetiological agent in chickenpox and shingles which can cause considerable human illness and suffering.
There has been considerable interest in the development of 5-substituted pyrimidine deoxynucleosides as putative antiviral agents.
Tetrahedron Letters, 22, 421, 1981, M. J. Robins and P. J. Barr describes a method of coupling terminal alkynes with protected 5-iodouracil nucleotides in the presence of a catalyst to give the corresponding 5-(alkyn-1-yl) uracil nucleosides.
J. Med. Chem. 26, 661, 1983, E. de Clercq, J. Descamps, J. Balzarini, J. Giziewicz, P. J. Barr and M. J. Robins describes a catalytic process for coupling terminal alkynes with 5-iodo-1-(2,3,5,-tri-O-p-toluyl-xcex2-D-arabinofuranosyl)uracil and 5-iodo-3xe2x80x2,5xe2x80x2-di-O-p-toluyl-2xe2x80x2-deoxyuridine. A cyclized by-product having methyl substituted at the 6-position was isolated and characterised spectroscopically.
J. Org. Chem. 48, 1854, 1983, M. J. Robins and P. J. Barr describes catalytic coupling of terminal alkynes with 5-iodo-1-methyluracil and 5-iodouracil nucleotides protected as their p-toluyl esters. The article also describes the conversion of 5-hexynyl-2xe2x80x2-deoxyuridine to cyclized 6-n-butyl-3-(2-deoxy-xcex2-D-erythro-pentofuraosyl)furano[2,3-d]pyrimidin-2-one.
Tetrahedron Letters 29, 5221, 1988, K. A. Cruickshank and D. L. Stockwell describes the catalytic condensation of 5xe2x80x2-dimethoxytrityl-5-iodo-2xe2x80x2-deoxyuridine with N-trifluoroacetyproparglyamine and subsequent conversion to the 3xe2x80x2-phosphoramidite.
J. Heterocyclic Chem. 28, 1917, 1991, R. Kumar, E. E. Knaus and L. I. Wiebe describes a reaction employing 5-(1-fluoro-2-bromoethyl)-3xe2x80x2,5xe2x80x2-di-O-acetyl-2xe2x80x2-deoxyuridine and producing a compound having the formula: 
J. Org. Chem. 1993, 58, 6614, G. T. Crisp and B. L. Flynn describes palladium catalysed couplings of terminal alkynes with a variety of oxyuridines. One coupling described is that between 5-ethynyl-2xe2x80x2-deoxyuridine and a range of fluorinated aryl compounds.
Nucleic Acids Research 1996, 24, 2470, J. Woo, R. B. Meyer and H. B. Gamper describes a process for the preparation of 3-(2xe2x80x2-deoxy-xcex2-D-ribofuranosyl)-pyrrolo-[2,3-d]-pyrimidine-2(3H)-one.
Can. J. Chem. 74, 1609, 1996, R. Kumar, L. I. Wiebe, E. E. Knaus describes a range of deoxyuridine compounds and their various anti-viral activity. A compound of the formula: 
was found to be inactive in the vitro assays against HSV-1, HSV-2, VZV and CMV.
JP 62255499 (Teijin Ltd) describes the preparation of fluorescent nucleosides or nucleotides and their use for DNA hybridization probes. The compounds described have the general formula: 
wherein X1 and Y1 are HO[P(O)(OH)O]n, Z1 is H or HO[P(O)(OH)O]m, with m and n=0 to 3, W1 is H or HO and R1 and R2 are H or C1 to C10 alkyl.
Nippon Kagaku Kaishi 7, 1214, 1987 describes the synthesis of fluorescent dodecadeoxy ribonucleotides having the general formula: 
where R can be H or butyl.
It is an object of the present invention to provide a novel class of nucleoside analogues.
It is a further object of the present invention to provide a novel class of nucleoside analogues for therapeutic use in the prophylaxis and treatment of viral infection for example by varicella zoster virus.
According to a first aspect of the present invention there is provided a compound having formula I as follows: 
wherein
R is selected from the group comprising C5 to C20 alkyl, C5 to C20 cycloalkyl, halogens, aryl and alkylaryl;
Rxe2x80x2 is selected from the group comprising hydrogen, alkyl, cycloalkyl, halogens, amino, alkylamino, dialkylamino, nitro, cyano, alkyoxy, aryloxy, thiol, alkylthiol, arylthiol, and aryl;
Rxe2x80x3 is selected from the group comprising hydrogen, alkyl, cycloalkyl, halogens, alkyloxy, aryloxy and aryl;
Q is selected from the group comprising O, S and CY2, where Y may be the same or different and is selected from H, alkyl and halogens;
X is selected from the group comprising O, NH, S, N-alkyl, (CH2)n where n is 1 to 10, and CY2 where Y may be the same or different and is selected from hydrogen, alkyl and halogens;
Z is selected from the group comprising O, S, NH and N-alkyl;
Uxe2x80x3 is H and Uxe2x80x2 is selected from H and CH2T, or Uxe2x80x2 and Uxe2x80x3 are joined so as to provide a ring moiety including Q wherein
Uxe2x80x2-Uxe2x80x3 together is respectively selected from the group comprising xe2x80x94CTHxe2x80x94CTxe2x80x2Txe2x80x3xe2x80x94 and xe2x80x94CTxe2x80x2xe2x95x90CTxe2x80x2xe2x80x94, so as to provide ring moieties selected from the group comprising 
xe2x80x83wherein
T is selected from the group comprising OH, H, halogens, O-alkyl, O-acyl, O-aryl, CN, NH2 and N3;
Txe2x80x2 is selected from the group comprising H and halogens and where more than one Txe2x80x2 is present they may be the same or different;
Txe2x80x3 is selected from the group comprising H and halogens; and
W is selected from the group comprising H, a phosphate group and a phosphonate group.
It is to be understood that the present invention extends to compounds according to formula I wherein the group W is modified to any pharmacologically acceptable salt or derivative of xe2x80x94H, phosphates or phosphonates. The present invention also includes any compound which is a pro-drug of the compound according to formula I, any such pro-drug being provided by modification of the moiety W, wherein W is selected from phosphates and derivatives thereof, and phosphonates and derivatives thereof.
Each of R, Rxe2x80x2 and Rxe2x80x3 may be substituted or unsubstituted and may be branched or unbranched. When any of R, Rxe2x80x2 and Rxe2x80x3 are alkyl or cycloalkyl they may be saturated or unsaturated. The nature, position and number of any substituents and unsaturation present may be varied. R may contain aryl or heteroaryl groups which may vary in nature, position or number. A preferred position is the terminus position in R. Examples of suitable substituents include OH, halogens, amino, CN, CHOH, CO2alkyl, CONH2, CONHalkyl, SH, S-alkyl and NO2, wherein alkyl is suitably C1 to C5. Suitably any substituent in R when R is alkyl or cycloalkyl is non-polar, more suitably any such substituent is additionally hydrophobic.
Preferably R is an alkyl group. More preferably R is a C7 to C20 alkyl group, which may optionally carry substituents such as halogens. Even more preferably R is a C8 to C14 group, particularly preferred is R being straight chain C10H21.
When R is aryl or alkylaryl it can be substituted. Alkylaryl can be aryl with one or more C1 to C10 groups attached which themselves can be substituted or unsubstituted. Aryl groups can include benzyl groups and heterosubstituted 5, 6 or 7 numbered rings. Either an aryl or an alkyl portion of an alkylaryl group can be attached to the ring structure. If desired R can, optionally substituted as above, for example be xe2x80x94(CH2)n-aryl-(CH2)mH, where n and m are each more than 1 and n+mxe2x89xa610 and the aryl is preferably C6H4. R cannot be any radical equivalent to 4-FC6H5, C6F5, 4 MeOC6H5, 3,5-(CF3)2C6H4, 3,5-F2C6H4, 4-CF3C6H5 or C6H5.
Suitably Rxe2x80x2 is selected from the group comprising C1 to C10 alkyl, C3 to C10 cycloalkyl, C1 to C10 alkylamino, C1 to C10 dialkylamino, C1 to C10 alkyloxy, C6 to C10 aryloxy, C1 to C10 alkylthiol, C6 to C10 arylthiol and C6 to C10 aryl. Suitably Rxe2x80x3 is selected from the group comprising C1 to C10 alkyl, C3 to C10 cycloakyl, C1 to C10 alkyloxy, C6 to C10 aryloxy and C6 to C10 aryl.
Preferably each of Rxe2x80x2 and Rxe2x80x3 is a small alkyl i.e. a C1 to C2 alkyl group or H. More preferably each of Rxe2x80x2 and Rxe2x80x3 is H.
Throughout the present specification xe2x80x9chalogenxe2x80x9d is taken to include any of F, Cl, Br and I.
Preferably Q is CH2, S or O. More preferably Q is O. Where Q is CY2 and includes a halogen, the halogen is preferably fluorine. Y is preferably H.
Preferably X is O, S or NH. More preferably X is O. Where X is (CH2)n, n is preferably 1 or 2, most preferably 1. X cannot be NH or N-alkyl when R is an unsubstituted C5 to C10 alkyl group, unless Q is other than O. Suitably when X is N-alkyl, alkyl is C1 to C5 alkyl and when X is CY2 at least one Y is C1 to C5 alkyl.
Preferably Z is O. Where Z is N-alkyl, suitably the alkyl is C1 to C5 alkyl.
Preferably Uxe2x80x2 and Uxe2x80x3 are joined to provide the saturated ring moiety including T, Txe2x80x2 and Txe2x80x3. Preferably T, Txe2x80x2 and Txe2x80x3 in such a ring moiety are respectively OH, H and H.
Preferably T is OH. When T is a halogen it is preferably F.
Preferably each of Txe2x80x2 and Txe2x80x3 is H. When either or both of Txe2x80x2 and Txe2x80x3 is halogen it is preferably fluorine.
When W is a moiety which renders the compound a pro-drug of the compound according to formula I it is to be understood that the term pro-drug includes the corresponding free base of each of the nucleosides described. The free base may moreover have direct antiviral action not dependent on metabolism to the corresponding nucleoside analogue.
It is also to be understood that xe2x80x9cphosphatexe2x80x9d includes diphosphates and triphosphates and xe2x80x9cphosphonatexe2x80x9d includes diphosphonates and triphosphonates. Hence W includes pharmacologically acceptable salts and derivatives of phosphates, diphosphates and triphosphates and of phosphonates, diphosphonates and triphosphonates. It also includes any moiety which provides a compound which is a pro-drug of the compound according to formula I, wherein W is selected from phosphates, diphosphates and triphosphates and derivatives thereof, and phosphonates, diphosphonates and triphosphonates and derivatives thereof.
Each compound may be the pure stereoisomer coupled at each of its chiral centres or it may be inverted at one or more of its chiral centres. It may be a single stereoisomer or a mixture of two or more stereoisomers. If it is a mixture the ratio may or may not be equimolar. Preferably the compound is a single stereoisomer. The compound may be in either enantiomeric form i.e. it may be either the D or L enantiomer either as a single stereoisomer or as a mixture of the two enantiomers. More preferably the compound has a stereochemistry resembling natural deoxy nucleosides derived from xcex2-D-2-deoxyribose. However other enantiomers particularly the L enantiomers may be employed.
It is to be understood that the present invention extends to compounds wherein the sugar moiety and phosphate if present have either together or separately been modified as well known to a person skilled in art.
It is also possible for a compound embodying the present invention to be in a sugar form as for example modified and derived from a D-xylo sugar system.
Particularly preferred compounds embodying the present invention have the following formulas: 
According to a further aspect of the present invention there is provided a method for preparing compounds having Formula I above wherein a 5-halo nucleoside analogue is contacted with a terminal alkyne in the presence of a catalyst. Alternatively 5-alkynyl nucleoside can be cyclised in the presence of a catalyst. Suitably the catalyst is a copper catalyst. The 5-alkynyl nucleoside has the general formula: 
Compounds embodying the present invention can show anti-viral activity. In particular it has surprisingly been found that compounds embodying the present invention can show antiviral activity against for example varicella zoster virus and/or cytomegalovirus.
According to a further aspect of the present invention there is provided a compound according to the present invention for use in a method of treatment, suitably in the prophylaxis or treatment of a viral infection. In this aspect of the present invention when X is NH or N-alkyl R can be C7 to C20 alkyl.
According to a further aspect of the present invention there is provided use of a compound according to the present invention in the manufacture of a medicament for the prophylaxis or treatment of viral infection. In this aspect of the present invention when X is NH or N alkyl R can be C7 to C20 alkyl.
According to a further aspect of the present invention there is provided a method of prophylaxis or treatment of viral infection comprising administration to a patient in need of such treatment an effective dose of a compound according to the present invention. In this aspect of the present invention when X is NH or N alkyl R can be C7 to C20 alkyl.
According to a further aspect of the present invention there is provided use of a compound of the present invention in the manufacture of a medicament for use in the prophylaxis or treatment of a viral infection, particularly an infection with the varicella zoster virus or an infection with cytomegalovirus. In this aspect of the present invention when X is NH or N alkyl R can be C7 to C20 alkyl. When the infection is the varicella zoster virus or cytomegalovirus then also in this aspect of the invention R can be aryl or alkylaryl, without the exclusion of R not being a radical equivalent to 4-FC6H5, C6H5, 4-MeOC6H5, 3,5(CF3)2C6H4, 3,5,-F2C6H4, 4-CF3C6H5 or C6H5.
According to a further aspect of the present invention there is provided a pharmaceutical composition comprising a compound of the present invention in combination with a pharmaceutically acceptable excipient. In this aspect of the invention when X is NH or N alkyl R can be C7 to C20 alkyl.
According to a further aspect of the present invention there is provided a method of preparing a pharmaceutical composition comprising the step of combining a compound of the present invention with a pharmaceutically acceptable excipient. In this aspect of the invention when X is NH or N alkyl R can be C7 to C20 alkyl.
The medicaments employed in the present invention can by administered by oral or parenteral routes, including intravenous, intramuscular, intraperitoneal, subcutaneous, transdermal, airway (aerosol), rectal, vaginal and topical (including buccal and sublingual) administration.
For oral administration, the compounds of the invention will generally be provided in the form of tablets or capsules, as a powder or granules, or as an aqueous solution or suspension.
Tablets for oral use may include the active ingredient mixed with pharmaceutically acceptable excipients such as inert diluents, disintegrating agents, binding agents, lubricating agents, sweetening agents, flavouring agents, colouring agents and preservatives. Suitable inert diluents include sodium and calcium carbonate, sodium and calcium phosphate, and lactose, while corn starch and alginic acid are suitable disintegrating agents. Binding agents may include starch and gelatin, while the lubricating agent, if present, will generally be magnesium stearate, stearic acid or talc. If desired, the tablets may be coated with a material such as glyceryl monostearate or glyceryl distearate, to delay absorption in the gastrointestinal tract.
Capsules for oral use include hard gelatin capsules in which the active ingredient is mixed with a solid diluent, and soft gelatin capsules wherein the active ingredient is mixed with water or an oil such as peanut oil, liquid paraffin or olive oil.
Formulations for rectal administration may be presented as a suppository with a suitable base comprising for example cocoa butter or a salicylate.
Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or spray formulations containing in addition to the active ingredient such carriers as are known in the art to be appropriate.
For intramuscular, intraperitoneal, subcutaneous and intravenous use, the compounds of the invention will generally be provided in sterile aqueous solutions or suspensions, buffered to an appropriate pH and isotonicity. Suitable aqueous vehicles include Ringer""s solution and isotonic sodium chloride. Aqueous suspensions according to the invention may include suspending agents such as cellulose derivatives, sodium alginate, polyvinyl-pyrrolidone and gum tragacanth, and a wetting agent such as lecithin. Suitable preservatives for aqueous suspensions include ethyl and n-propyl p-hydroxybenzoate.
The compounds of the invention may also be presented as liposome formulations.
In general a suitable dose will be in the range of 0.1 to 300 mg per kilogram body weight of the recipient per day, preferably in the range of 1 to 25 mg per kilogram body weight per day and most preferably in the range 5 to 10 mg per kilogram body weight per day. The desired dose is preferably presented as two, three, four, five or six or more sub-doses administered at appropriate intervals throughout the day. These sub-doses may be administered in unit dosage forms, for example, containing 10 to 1500 mg, preferably 20 to 1000 mg, and most preferably 50 to 700 mg of active ingredient per unit dosage form.
Embodiments of the present invention will now be described by way of example only. It will be appreciated that modifications to detail may be made whilst still falling within the scope of the invention.
Experimental
In the following examples the bicyclic rings of the compounds are numbered following recommended IUPAC guidelines. Thus 3-(2xe2x80x2-Deoxy-xcex2-D-ribofuranosyl)-6-octyl-2,3-dihydrofuro[2,3-d]pyrimidin-2-one has the structure and is numbered as follows: 
To a stirred solution of 5-iodo-2xe2x80x2-deoxyuridine (800 mg, 2.26 mmol) in dry dimethylformaldehyde (8 ml), at room temperature under a nitrogen atmosphere, was added dry diisopropylethylamine (584 mg, 0.80 ml, 4.52 mmol), 1-decyne (937 mg, 1.22 ml, 6.78 mmol), tetrakis (triphenylphosphine) palladium (0) (261 mg, 0.226 mmol) and copper (I) iodide (86 mg, 0.452 mmol). The reaction mixture was stirred at room temperature for 19 hours, after which time the reaction mixture was concentrated in vacuo. The resulting residue was dissolved in dichloromethane/methanol (1:1) (6 ml) and an excess of Amberlite IRA-400 (HCO3xe2x88x92 form) was added and the mixture was stirred for 30 minutes. The resin was then filtered, washed with methanol and the combined filtrate was evaporated to dryness. The crude product was purified by silica gel column chromatography using an initial eluent of ethyl acetate, then changing to ethyl acetate/methanol (9:1) via a gradient. The appropriate fractions were combined and the solvent removed in vacuo to yield the product as a cream solid (490 mg, 60%). Recrystallization of the product from hot dichloromethane yielded the pure product as fine white crystals (376 mg, 46%).
1H-nmr (d6-DMSO;300 MHz): 11.56(1H, br.s, NH-3), 8.11(1H, s, H-6), 6.12(1H, dd, 3J=6.6 Hz, H-1xe2x80x2), 5.25(1H, d, 3J=4.2 Hz, 3xe2x80x2-OH), 5.09(1H, t, 5xe2x80x2-OH), 4.24(1H, m, H-3xe2x80x2), 3.79(1H, m, H-4xe2x80x2), 3.59(2H, m, H-5xe2x80x2), 2.36(2H, t, 3J=6.8 Hz, xcex1-CH2), 2.12(2H, m, H-2xe2x80x2a and H-2xe2x80x2b), 1.47(2H, m, xcex2-CH2), 1.38-1.26(10H, m, 5xc3x97CH2), 0.87 (3H, t, CH3). 13C-nmr (d6-DMSO; 75 MHz): 16.2(CH3), 21.0, 24.3, 30.4, 30.5, 30.8, 30.9(6xc3x97CH2), 33.5(xcex1-CH2), 41.7(C-2xe2x80x2), 63.2(C-5xe2x80x2), 72.4(C-3xe2x80x2), 75.1, 86.8, 89.8, 95.5(C-4xe2x80x2, C-xcex2, C-1xe2x80x2, C-xcex1), 101,3(C-5), 144.9(C-6), 151.7(C-2), 164.0(C-4). Mass spectrum (ESxe2x88x92MS(+ve)): 387[M+Na]+, 365[M+H]+.
All 1H and 13C-NMR spectra were recorded on a Bruker Avance DPX300 spectrometer at 300 MHz and 75 MHz respectively. Chemical shifts were recorded in parts per million (ppm) downfield from tetramethylsilane.
Low resolution mass spectra were recorded on a Fisons Instruments VG Platform Electrospray mass spectrometer run in either positive or negative ion mode, with acetronitrile/water as the mobile phase.